TC1784
LMB External Bus Unit
User´s Manual
12-27
V1.1, 2011-05
EBUT13L-A, V1.16
•
Returns the asserted CS high if the access is a read or the length of the Data Hold
Phase is zero.
12.9.5
Data Hold Phase (DH)
The Data Hold phase is optional. This means that it can also be programmed for a length
of zero EBU_CLK clock cycles. Furthermore, it is only available for asynchronous write
accesses. The Data Hold phase extends the amount of time for which data is still held
on the bus after the rising edge of the RD/WR signal occurred. The Data Hold phase is
used to accommodate external devices that require a data hold time after the rising edge
of the RD/WR signal. The length (number of EBU_CLK cycles) of the Data Hold phase
is programmed via the EBU_BUSAPx.DATAC bit field.
At the end of the Data Hold Phase, the EBU will:
•
Remove the write data from the data bus (in the case of a write cycle),
•
Return the CS high.
Note: If an attached asynchronous memory device latches write data on the rising edge
of any of the control lines; CS, RD/WR or BC, then a Data Hold phase will be
required to ensure that data is latched correctly.
12.9.6
Recovery Phase (RP)
The Recovery Phase is optional (although for access types which would cause a bus
contention a single cycle of recovery is normally forced by the memory controller logic).
This means that it can also be programmed for a length of zero EBU_CLK clock cycles.
This phase allows the insertion of a delay following an external bus access that delays
the start of the Address Phase for the next external bus access. This permits flexible
adjustment of the delay between accesses to the various external devices. The following
individually programmable delays are provided on a region by region basis for the
following conditions:
•
Bit fields EBU_BUSAPx.RDRECOVC determine the basic length of the Recovery
Phase after a read access.
•
Bit fields EBU_BUSAPx.WRRECOVC determine the basic length of the Recovery
Phase after a write access.
•
Bit fields EBU_BUSAPx.DTACS determine the length (basic number of EBU_CLK
clock cycles) of the Recovery Phase after a read/write access of one region that is
followed by a read/write access of another region or a read to one region is followed
by a write to the same region (BUSRAPx.DTACS) or a write to one region is followed
by a read to the same region (BUSWAPx.DTACS).
The EBU implements a “highest wins” algorithm to ensure that the longest applicable
recovery delay is always used between consecutive accesses to the external bus.
shows the scheme for determining this delay for all possible circumstances.
For example, if a read access to a region associated with CS1 is followed by a write to
Содержание TC1784
Страница 1: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Страница 3: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Страница 950: ...TC1784 Direct Memory Access Controller DMA User s Manual 11 132 V1 1 2011 05 DMA V3 03 ...
Страница 1949: ...TC1784 General Purpose Timer Array GPTA v5 User s Manual 21 297 V1 1 2011 05 GPTA v5 V1 14 ...
Страница 2350: ...w w w i n f i n e o n c o m Published by Infineon Technologies AG Doc_Number ...